1. Field of the Invention
This invention relates to the dyeing of carpets and, more particularly, to a method and apparatus for dyeing carpets which, through the use of a dye bath which has a much higher boiling point than water, does not require the steaming of the carpet to set or fix the dye to the carpet.
2. Prior Art
Currently known and used methods and apparatuses for dyeing carpet require the steaming of the carpet to set or fix the dye to the carpet after the dye has been applied to the carpet. For example, the typical carpet dyeing method and apparatus involves the application of a dye to the pile surface of the carpet, fixing the dye onto the carpet pile by steaming and then subjecting the carpet to various other finishing procedures Prior to drying the carpet.
Once such conventional carpet dyeing process is disclosed in U.S. Pat. No. 4,101,270. This patent discloses a method for dyeing carpet which includes the steps of advancing a continuous textile web through a preshrinking station, moistening the textile web, dyeing the textile web using applicator rolls and/or dye applicators, and then fixing the dye onto the textile web by passage through, for example, a chamber containing steam. This basic method generally forms the base for the other prior art carpet dyeing systems and is well known in the art.
Likewise, a second example of a carpet dyeing process including a steam fixator is disclosed in U.S. Pat. No. 4,771,497. This patent discloses a process for the continuous treatment of a textile web material involving the application of a dye to the pile surface of the carpet and then initiating the dye fixation onto the pile surface by steaming. Many of the prior art patents such as the two disclosed above involve such a steam fixation process and are distinguishable from each other by various additional, optional processes added onto this base dyeing technique.
The patent issued to Walter, U.S. Pat. No. 2,387,200, discloses and claims a method for dyeing material which is carried out in a sealed chamber, namely a closed chamber incorporating compressed air and saturated steam. The '200 method is carried out at a temperature substantially above 212.degree. F. and under pressure. Therefore, the '200 method incorporates by its nature a steam fixation step as when the material emerges from the dye bath which is heated substantially above 212.degree. F., it encounters compressed air and saturated steam under pressure, which is the equivalent of a steam fixation step. The apparatus of the present invention is not a closed or sealed chamber, but is open to the atmosphere, and does not use water-based dye baths or steam, thus eliminating the steam fixation step which can cause uneven dyeing and running of the dye. Further, the use of an open chamber and lower overall temperatures, namely typically between 212.degree. F. and 240.degree. F., allows the present invention to be much more economical in terms of energy costs and apparatus material costs.
The method disclosed in the '200 patent also does not comprise a separate, independent material preheating step, nor the means for carrying out such a separate, independent material preheating step. The material to be dyed in the '200 method is introduced to the pressure chamber and almost immediately submerged into the dye bath. Although the material to be dyed encounters elevated temperatures upon being introduced to the pressure chamber, no specific control or methodology is present to constitute a preheating step or means. In the present invention, a separate, independent preheating step accomplished by a separate, independent preheating means is carried out on the material to be dyed prior to the introduction of the material to be dyed to the main dye bath. The controlled preheating of the material to be dyed to a temperature near or at the temperature of the dye bath helps to reduce the dye application time and the heat loss from the dye bath which would occur if the material to be dyed needed to be heated to the temperature of the dye bath during the dyeing process. Such a separate, independent preheating step and means, which may utilize the same heat source as the dye bath, has economic advantages over prior art processes, such as that disclosed in the '200 patent.
The patent to von der Eltz et al., U.S. Pat. No. 3,986,831, discloses and claims a high temperature, high pressure batch process for dyeing materials which incorporates a pressure vessel and high-pressure steam fixation. The '831 apparatus and method operate in an essentially air-free environment. Further, the dye fixation disclosed in the '831 patent occurs at a temperature over about 255.degree. F., creating the need for significant energy input. Likewise, the patent to Blount, U.S. Pat. No. 3,418,065, discloses and claims a high temperature, high pressure batch process which also is carried out in a sealed pressure chamber not open to the atmosphere and which incorporates a steam fixation step. On the contrary, the present process and apparatus are open to the atmosphere and do not involve the use of steam or steam fixation. The present process is a continuous process which is carried out on a continuous-running apparatus. Further, the entire process of the present invention can occur at a temperature of between 212.degree. F. and about 240.degree. F. significantly reducing the energy costs and the apparatus costs.
The disadvantages of such prior art carpet dyeing methods and apparatuses which incorporate steam fixation components is the necessity for the steam fixation step. Steam fixation has several disadvantages including the need for a tremendous amount of energy required to heat the steam, dilution of the dye as the steam condenses into water and mixes with the dye, and the cost of the equipment, both in material and time, needed to have a steam fixation step in the carpet dyeing process. A further disadvantage is that a carpet dyeing process including a steam fixation step is uneconomical to operate when dyeing small batches of carpet.
The development of the open-to-the-atmosphere process and apparatus also allows for the dyeing of materials at significantly lower energy costs and with a higher degree of safety. Less energy is necessary as there are no materials to be superheated and no pressure needs to be created. Materials costs are reduced as vessels open to the atmosphere typically do not need the reinforcing required for a pressure vessel. Lastly, pressure operations typically inherently are more dangerous than an equivalent atmospheric operation.